Method of producing a strip of lead frames for integrated circuit dies in a continuous system

A continuous method for producing a strip of lead frames for integrated circuit dies, comprising

• feeding continuously a strip of platable material for making a strip of lead frames so that the strip serves as a substrate having upper and lower faces,
• cleaning and preparing the substrate for plating with copper,
• plating both faces of the substrate with copper in a continuous manner to a thickness of 5 to 10 microinches,
• selectively silver plating the upper faces of the substrate to a thickness of 100 to 150 microinches,
• simultaneously laminating both faces of the substrate with a photosensitive film,
• exposing selected portions of the film to high intensity light and developing the exposed film which is retained on the strip as a resist film and washing away the unexposed, undeveloped film to reveal the outlines of a mini strip of six lead frames,
• removing any exposed silver from the substrate,
• removing the exposed area of the substrate by etching the substrate in FeC.sub.13,
• stripping any silver edges overhanging,
• removing the resist film,
• removing any exposed copper plating from the substrate and retaining any copper covered by the silver plating,
• rinsing the substrate clean and air drying it, and
• taping, downsetting, cutting and packing the substrate into mini strips of six lead frames.

A continuous method of producing a strip of lead frames for integrated circuit dies, comprising the steps of

• preplating a continuously fed substrate with silver at predetermined spot locations,
• thereafter stopping and applying to the continuously fed substrate a photo-sensitive film and a photo-mask having a predetermined design,
• exposing the film while the substrate is stopped but nevertheless being continuously fed to form an opaque design,
• developing the film,
• removing the film around the design to expose an unwanted portion of the silver and an unwanted portion of the substrate,
• removing said exposed silver,
• and etching away said exposed portion of the substrate to form the lead frames.